Process for making tubing



June 4, 1946. c. BOOTH PROCESS FOR MAKING TUBING Filed April 3, 1.944

- INVEN'EFOR. 59m. Cifloonr,

Patented June 4; 1946 UNITED. 1 STATES PATENTTOFFICE PRocEss FOR-"MAKINGTUBING Earl C. Booth, Columbus, Ind; assignor to Noblitt-Spark'sIndustries, Inc., -I nd., a corporation of Indiana Columbus,

, Application April 3, 1944, Serial No. 529,348

This invention relates to tubularmetallicarti cles and more particularlyto a process for producing them. My object is toreduce the cost ofmanufacture of such articles and to increase about its axisthat the loadwill be applied in the plane of the web; and if, the tubingis bent informing the finished article, the bendingis preferably done in the planeof the web.

The accompanying drawing illustrates my invention. Fig. 1 is a sideelevation ofa chair embodying tubular supporting elements formed inaccordance withmy invention; Fig. 2 is a transverse section on the line22 of Fig, 1; Fig.3 is a transverse section of an extruded stripsuitable for use in forming the tube shown in Fig, 2; ,Fig.

" 4 is a transverse section through a modifiedform of tube; Figs. 5 and6 are .transversesections of alternative strips suitable for use informing the tube of Fig.4; Fig. 7 is a section similar to Fig, 2illustrating a further modification; Figs, 8 and 9 are transversesections illustrating alternative strips suitable for use in forming thetube of Fig. 7; and Fig. 10 is a transverse section similar to Fig. 2showing a tube formed of flat strip stock.

The chair illustrated in Fig. 1 is shown merely to illustrate one usefor m invention and embodies supporting members [5 formed of metaltubing and located at opposite sides of the chair. The tubing of whichthe member I5 is formed is circular in section and embodies interiorly adiametrically extending web.

The tube shown in Fig. 2 is conveniently formed from a metal striphaving the cross-sectional shape illustrated in Fig. 3. Such strip has acentral portion l6, which may be approximately plane, side orintermediate portions l1; and edge portions l8. The portions H aredesirably curved on a radius equal to the radius of curvature of. thecylindrical wall in the finished tube. The edge portions l8 are plane.Desirably, the interior of the junction between each curved portion I!and the adjacent plane portion 18 is 4 Claims. (Cl. 29-156) a r 2 rformed. with arather generous fillet 20, while exteriorly such junctionis characterized by a well-defined edge 'Zl representing theintersection of the mutually perpendicular outer surfaces of theportions I .1 and I8. The strip of Fig. 3 is desirab ly formed ofaluminum, aluminum alloy, or similarmetal by extrusion.

In forming a tube from astrip of the crosssectionillustrated in Fig. 3,the center portion of th strip is curved transversely, to bring theedges2I -2l together with the opposedfaces of the edge'portions l8 in contactwith each other to form a diametrically extending web, as shown in Fig.2. To complete the tubing, the edge 2l-2| are welded together, andthefree edge of the Web formed by the portions l8l8 is welded to thecenter portion It at the point indicated at 22 in Fig. 2. 1 Such weldingneed not be continuous,, and is desirably carried out by thecondenser-type process.

In the tubin illustrated in .Fig. 4, the center web 25. is, of singlethickness. be formed of an extruded strip having a generall T-shapedcross-section similar to those illustrated in Figs. 5 and 6.. In Fig. 5,the center web 25 is united along one edge with two oppositelyprojecting. flanges. Adjacent the web '25, the flanges are curved incross-section as indicated at 26, desirably to thecurvature of thecylindrical wall of the. tubing in Fig. 4; while beyond such curvedportions the flanges are approximately plane, as indicated at 21. Thejunction of the web 25 with each curved flange-portion 26 ischaracterized by an interior fillet 28.

In forming a tube of the strip shown in Fig. 5, the relatively planeflange-portions 21 ar curved to abut each other over the free edge ofthe web 25, as will be clear from Fig. 4; and the abutting flange-edgesare then welded together and to the adjacent edge of the web 25.

The strip illustrated in Fig. 6 is similar to that shown in Fig. 5except that the flanges have their relatively plane portions 30 locatednear their junctions with the flange 25 and their outer edges curved asindicated at 3|. In forming a tube of the strip of Fig. 6, theflange-portions 30 are curved to bring the free edges of the portions 3|together above the free edge of the web 25, and all such edges are thenwelded together.

The tube illustrated in Fig. 7 resembles that shown in Fig. 4 exceptthat the flanges forming the cylindrical tubewal1 are unitedrespectively with opposite edges of the center web 25. Such a tubing maybe formed of a strip having the general Z-shaped cross-sectionillustrated in Fig. 8;

This tubing may I In that strip, the two flanges are joined respec- 4ing embodies but one joint or seam visible'irom' the exterior, as is thecase in the tubes of Figs. 3 and 10, the joint is desirably disposed onthe inside of the bend where it will be least conspicuous.

I claim as my invention: 1. A process of forming metal tubing having a.transversely extending, interior web, which comprises extruding metal toproduce an integral to the strip shown in Fig. 8 except thatthe plane vportions 38 of the flanges are located adjacent the web while the edgeportions are curved as indicated at 39.

The extrusion process, v I in producing the strip of which my tubing isformed, has the advantage that it produces a strip admirably suited tothe production of tu'b-' ing of attractive appearance. Desirably, alarge.

part of the transverse extent of the strip-portions which are toconstitute thecylindrical tube-wall are formedin the extrusion processto have a curvature corresponding to the curvature of that wall. This,reduces the amount of transverse bending whic'h niust be performed inconvertin the stripinto a tube. Further, strip-portions whoseform"cannot be readily changed in the operation of converting the stripinto a. tube may be forrned' byfthe extrusion process to have acurvature corresponding to that of the outer surface of thefinishedtube. Examples'of such'stripportions are those'adjacent theedges 2| in Fig. 2 and those adjacentthe bases of the webs and indicatedat 32 inFigs. 6, 8,-and 9. Again, the extrusion process permits theformation of relatively sharp edges on portions which are to be joinedto others in the'finished tube and thus aids in makingthe'jointrelatively inconspicuous. 'The tube shown-*in Fig. 10' is madeof flat strip-stock having a center portion .4! transversely curvedtoform the'cylindrical tube wall and edge portions "bent in'war'dlyandlying in juxtaposed'relation to fori'n the reinforcing web. The edges ofthe central portion are secured toat the'point 44. I

In formingthe chair-supporting element I? from any of the tubesdescribed; the tube is converted into the desired shape by bending it inthe plane ot the interior web. In such bending, the web is preventedfrom buckling by reason of thefact that both its longitudinal edges ares'e-- cured to the tube-wall, and the web adds greatly to the strengthof the element. Where the tub- 'which I prefer to use elongated striphaving wall-forming and webforming portions, parts of each wall-formingportion and the junction of the-.:.web-forming and wall-forming portionsbeing shaped in the ex-- trusion to the cross-sectional form they are to.possess in the finished tubing, curving the other partorparts of eachwall-forming portion to form a closed tube across the interior of whichtheweb-forming portion extends diametrically with its edge in contactwith a, wall-forming portion, and then welding such web-edge andwallforming portion together.

2. A process of forming metal tubing having a transversely extending,interior web, which comprises extruding metal to produce an integralelongated strip having a central, Plane, 'webforming portion andsymmetrical wall-forming portions extending in opposite directions fromone edge of said,'web-forming portions, a, part of each wall-formingportionjand the junction of the web-forming 'and wall-forming portionsbemgsna ed inthe extrusion to the cross-sectional shape they areto'havein the finished tubing,

I curving the other part of each wall-forming portion to form a closedtube with the free edges of the wall-forming portions meeting at thefree edge of the web-forming portion, and then welding such free edgestogether.

3. A process of forming metal tubing having a gether by welding at thepoint 43,"and theffree edge of'the webis welded to'the cylindrical wallprises'extruding metal to produce an integral elongated, strip having acentral, plane, webformi'ng portion and symmetrical wall-formingportions extending in opposite directions from one edge of saidweb-forming portions, the junction of the web-forming and wall-formingportions being shaped in the extrusion to the crosssectional shape theyare to have in the finished tubing, curving each wall-forming portion toform a'closedtube with the free edges of the wall forming-portionsmeeting at the free edge of the web-forming portion, and then weldingsuch free edges together.

'4. The process set forth in claim 1' with the further step of bendingthe tubing. in the plane EARL C. BOOTH.

